1. Field of the Invention
The present invention relates to the field of detecting bio-electric activity of tissue.
2. Prior Art
Using modern ECG monitors to determine, for instance, when an electrode is in contact with live contractile heart tissue, to differentiate live from dead contractile heart tissue or to localize Purkinje fibers is difficult using modern ECG monitors because there is little difference in displayed signal amplitudes between when an electrode is very near, nearing, moving further away from, in contact with or a few centimeters away from an electrically active tissue.
The reason for this lack of significant change in signal amplitudes is the high input impedance of modern ECG and other bio-electrical activity monitors. For instance, an input impedance/resistance of 1012 ohms is not unusual for an input amplifier of a monitor. Of course, for monitoring purposes, this high input impedance is desirable, as the signal levels are thus as high and as constant as possible, allowing standardized monitoring procedures and diagnosis despite variations in sensing electrode placement or electrode impedance. Also, the gain range in the monitors may be smaller and gain adjustment is often not necessary to obtain a well-defined signal. From a historical perspective, the development of higher input impedance amplifiers also improved patient safety by reducing leakage currents and the like.